As a production method of turbine blade, conventionally, a method of producing turbine blade by shaving it out of a block material one by one has been generally conducted.
However, in a case where the turbine blade is shaved out of the block material, there is such a problem that an amount of work is large, a yield of material is poor, and besides, a long time is required for the work, and it is difficult to enhance productivity.
On the other hand, a method of producing turbine blade as a single body by forging is also known. For example, forging and forming a turbine blade as a single body is disclosed in the following Patent Documents 1 and 2.
However, in a case where the turbine blades are forged as single bodies in this manner, and respectively subjected to machining, the number of processes required for forging is increased, and the number of processes of the machining thereafter is also increased.
Specifically, in case where the turbine blades which have been forged are subjected to machining, setups for the machining are first conducted, then, the machining is conducted, and thereafter, machined products are taken out. In this case, a series of processes for the machining must be carried out for each of the turbine blades which have been forged, and therefore, a lot of troubles and time are required for the machining.    Patent Document 1: Japanese Patent Publication No. JP-A-2-80149    Patent Document 2: Japanese Patent Publication No. JP-A-63-112039